Nutrient Recovery Technologies Research Articles

Nitrogen and Phosphorus Recovery from Anthropogenic Liquid Waste Streams

Nutrient recovery from waste is a promising strategy to conserve inputs while reducing nutrient discharge to the natural environment. Multiple waste streams have shown promise with respect to nutrient recovery. Multiple technologies also show promise at a pilot or full scale. These technologies, however, must not exacerbate other environmental issues, with excessive energy use, unsustainable material extraction (e.g., mineral extraction, cement use), or toxin release into the environment. Such technologies must also be feasible from economic and social perspectives. Work, therefore, should focus on both improving our current suite of available technologies for nutrient recovery from waste and framing policies that blend affordability with incentives, thereby fostering an environment conducive to innovation and adoption of sustainable approaches. This review considers the issues associated with nutrient recovery from waste, including technical feasibility and economic, environmental, and social factors, and identifies current knowledge gaps and emerging opportunities for nutrient waste recovery.

A nutrient circular economy framework for wastewater treatment plants

Given the criticality of phosphorous and the harm eutrophication causes, wastewater treatment plants (WWTP) are undergoing circular economy (CE) conversions into becoming centres for resource recovery. This framework paper identifies the environmental, societal, political, commercial, economic, consumer, regulatory, legal, infrastructural, technological, international compliance, academic, agricultural, and plant-operator factors affecting the micro, macro and meso success and failure of nutrient CE WWTP across scope classifications. From this, nutrient CE framework is not as simplistic as it looks, given the multitude of impingers that need to be considered. The lack of technological readiness and vast selection methodologies for some nutrient recovery technologies, low private-sector investment, divisive consumer perceptions, unique economic situations, localised regulatory specifications, threats of inefficient technology lock-ins, poor acceptance among farmers and WWTP operators due to infrastructural incompatibilities, lack of efficient CE supply chains, legacy infrastructure, poor digitised solutions for nutrient CE management, low training and awareness, and integration of nutrient CE WWTPs with broader society are barriers. On the contrary, nutrient CE WWTP will mainly be driven by regulations, subsidies and consumer-WWTP-farmer nutrient CE acceptances. This framework aims to tie in and provide solutions to overcoming barriers to nutrient CE WWTPs that is universally applicable. Consequently, the framework provides a holistic structure for policy, legislative, academic, agricultural, plant operators, commercial and consumer stakeholders a roadmap for the success and difficulties of nutrient CE WWTP adoption.

Hydrogel Applications in Nitrogen and Phosphorus Compounds Recovery from Water and Wastewater: An Overview

This article provides an overview of the diverse applications of hydrogels in nutrient recovery from water and wastewater. Due to their unique properties, such as high water-retention capacity, nutrient rerelease, and tunable porosity, hydrogels have emerged as promising materials for efficient nutrient capture and recycling. It has been suggested that hydrogels, depending on their composition, can be reused in agriculture, especially in drought-prone areas. Further research paths have been identified that could expand their application in these regions. However, the main focus of the article is to highlight the current gaps in understanding how hydrogels bind nitrogen and phosphorus compounds. The study underscores the need for research that specifically examines how different components of hydrogel matrices interact with each other and with recovered nutrients. Furthermore, it is essential to assess how various nutrient-recovery parameters, such as temperature, pH, and heavy metal content, interact with each other and with specific matrix compositions. This type of research is crucial for enhancing both the recovery efficiency and selectivity of these hydrogels, which are critical for advancing nutrient-recovery technologies and agricultural applications. A comprehensive research approach involves using structured research methodologies and optimization techniques to streamline studies and identify crucial relationships.

Phosphorus recovery via struvite crystallization in batch and fluidized-bed reactors: Roles of microplastics and dissolved organic matter

Struvite crystallization, a promising technology for nutrient recovery from wastewater, is facing considerable challenges due to the presence of emerging contaminants such as microplastics (MPs) ubiquitously found in wastewater. Here, we investigate the roles of MPs and humic acid (HA) in struvite crystallization in batch and fluidized-bed reactors (FBRs) using synthetic and real wastewater with a Mg:N:P molar ratio of 1:3:(1–1.3) at an initial pH of 11. Batch reactor (BR) experiment results show that MPs expedited the nucleation and growth rates of struvite (e.g., the rate of crystal growth in the presence of 30 mg L−1 of polyethylene terephthalate (PET) was 1.43 times higher than that in the blank system), while HA hindered the formation of struvite. X-ray diffraction and the Rietveld refinement analysis revealed that the presence of MPs and HA can result in significant changes in phase compositions of the reclaimed precipitates, with over 80 % purity of struvite found in the precipitates from suspensions in the presence of 30 mg L−1 of MPs. Further characterizations demonstrated that MPs act as seeds of struvite nucleation, spurring the formation of well-defined struvite, while HA favors the formation of newberyite rather than struvite in both reactors. These findings highlight the need for a more comprehensive understanding of the interactions between emerging contaminants and struvite crystallization processes to optimize nutrient recovery strategies for mitigating their adverse impact on the quality and yield of struvite-based fertilizers. Environmental ImplicationThe presence of microplastics in wastewater poses a significant challenge to struvite crystallization for nutrient recovery, as it accelerates nucleation and growth rates of struvite crystals. This can lead to changes in the phase compositions of the reclaimed precipitates, with implications for the quality and yield of struvite-based fertilizers. Additionally, the presence of humic acid hinders the formation of struvite, favoring the formation of other minerals like newberyite. Understanding the interactions between emerging contaminants and struvite crystallization processes is crucial for optimizing nutrient recovery strategies and mitigating the environmental impact of these contaminants on water quality and struvite-based fertilizers.

Kinetic study of magnesium dissolution using a magnesium oxide industrial by-product

Phosphorus recovery via struvite precipitation in wastewater treatment plants (WWTPs) is a key technology for nutrient recovery. This work investigates the dissolution kinetics of an industrial low-grade magnesium oxide (LG-MgO) by-product as an alternative to common magnesium sources for struvite precipitation. The main aims were to develop a parsimonious dissolution kinetic model capable of predicting the release of magnesium into the solution with accuracy and studying the influence of temperature on dissolution kinetics. The simultaneous fitting of all the experiments by non-linear regression rendered overall process values of the dissolution model’s frequency factor (498,606 L3.22 min−1 mmol−1.74), activation energy (37.51 kJ·mol−1), and reaction order (2.74). The goodness-of-fit for all experiments was evaluated by the total sum of squared residuals and R2 coefficients, being excellent under all conditions. The estimated kinetic coefficient values showed a temperature-dependent variation of the kinetic coefficient, increasing from 0.079 to 0.219 L3.22 min−1 mmol−1.74 when the temperature increased from 15 to 35 °C. The magnesium dissolution was fast in the first 5 min, where 40–78 % of magnesium dissolved with respect to the initial magnesium in the solid. Despite the assumptions made in the model derivation, the developed kinetic model provides a practical, reliable, and easy-to-use tool for WWTPs to estimate the LG-MgO dosage required to achieve targeted magnesium concentrations, thereby improving reagent use efficiency and phosphorus recovery.

Intensive Microalgal Cultivation and Tertiary Phosphorus Recovery from Wastewaters via the EcoRecover Process.

Mixed community microalgal wastewater treatment technologies have the potential to advance the limits of technology for biological nutrient recovery while producing a renewable carbon feedstock, but a deeper understanding of their performance is required for system optimization and control. In this study, we characterized the performance of a 568 m3·day-1 Clearas EcoRecover system for tertiary phosphorus removal (and recovery as biomass) at an operating water resource recovery facility (WRRF). The process consists of a (dark) mix tank, photobioreactors (PBRs), and a membrane tank with ultrafiltration membranes for the separation of hydraulic and solids residence times. Through continuous online monitoring, long-term on-site monitoring, and on-site batch experiments, we demonstrate (i) the importance of carbohydrate storage in PBRs to support phosphorus uptake under dark conditions in the mix tank and (ii) the potential for polyphosphate accumulation in the mixed algal communities. Over a 3-month winter period with limited outside influences (e.g., no major upstream process changes), the effluent total phosphorus (TP) concentration was 0.03 ± 0.03 mg-P·L-1 (0.01 ± 0.02 mg-P·L-1 orthophosphate). Core microbial community taxa included Chlorella spp., Scenedesmus spp., and Monoraphidium spp., and key indicators of stable performance included near-neutral pH, sufficient alkalinity, and a diel rhythm in dissolved oxygen.

Bioponic systems with biochar: Insights into nutrient recovery, heavy metal reduction, and microbial interactions in digestate-based bioponics

Bioponics is a nutrient-recovery technology that transforms nutrient-rich organic waste into plant biomass/bioproducts. Integrating biochar with digestate from anaerobic wastewater treatment process can improve resource recovery while mitigating heavy metal contamination. The overarching goal of this study was to investigate the application of biochar in digestate-based bioponics, focusing on its efficacy in nutrient recovery and heavy metal removal, while also exploring the microbial community dynamics. In this study, biochar was applied at 50 % w/w with 500 g dry weight of digestate during two 28-day crop cycles (uncontrolled pH and pH 5.5) using white stem pak choi (Brassica rapa var. chinensis) as a model crop. The results showed that the digestate provided sufficient phosphorus and nitrogen, supporting plant growth. Biochar amendment improved plant yield and phosphate solubilization and reduced nitrogen loss, especially at the pH 5.5. Furthermore, biochar reduced the heavy metal accumulation in plants, while concentrating these metals in the residual sludge. However, owing to potential non-carcinogenic and carcinogenic health risks, it is still not recommended to directly consume plants cultivated in digestate-based bioponic systems. Additionally, biochar amendment exhibited pronounced impact on the microbial community, promoting microbes responsible for nutrient solubilization and cycling (e.g., Tetrasphaera, Herpetosiphon, Hyphomicrobium, and Pseudorhodoplanes) and heavy metal stabilization (e.g., Leptolinea, Fonticella, Romboutsia, and Desulfurispora) in both the residual sludge and plants. Overall, the addition of biochar enhanced the microbial community and facilitated the metal stabilization and the cycling of nutrients within both residual sludge and root systems, thereby improving the overall efficiency of the bioponics.

Combination of technologies for nutrient recovery from wastewater: A review

The growing human population is increasing the need for crop production, which has resulted in elevated requirements of Nitrogen-Phosphorous-Potassium (NPK) fertilisers. This tremendous demand cannot be sustained on traditional processes, which cause significant resource depletion and unacceptable environmental impacts due to their heavy reliance on fossil fuels. To overcome this, alternative sources to obtain fertilisers have been explored, including the recovery of nutrients from wastewater and waste streams. However, this approach faces several challenges, such as the dilution of the streams, low public acceptance, and lack of support. With the aim of surpassing these barriers, the present study provides a review of existing Research & Development (R&D) projects in the field, comparing the available technologies to identify the optimal train of technologies for nutrient recovery: Anaerobic Digestion followed by the valorisation of the digestate (directly or producing P-based fertilisers such as P salts, CaP, H3PO4 and P2O5) and the liquid fraction (obtaining struvite, ammonium sulphate/nitrate, and reclaimed water). Moreover, an innovative strategy for nutrient recovery based on the decentralised treatment of separated concentrated streams is proposed as a useful strategy for valorising nutrients, developing a Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis. Finally, non-technological strategies are suggested to mainstream waste valorisation, aimed at overcoming social barriers by promoting stakeholder acceptance and producing recycled fertilisers with low associated rejection. Nutrient valorisation through the decentralised treatment of source separated waste/wastewater using optimised train of technologies seems a sustainable strategy for addressing the current and future massive demand of fertilisers.

Improving BioWin Modeling of Phosphorus Solubilization in Acid-Phase Digesters

BioWin 6.0 does not accurately predict phosphorus (P) speciation in acidogenic anaerobic digesters under default kinetics characterization and parameterization. The accurate modeling of acid-phase digestion is needed to predict the performance of novel nutrient recovery technologies that act on these digester effluents. The main thrust of this work was to identify and correct the causes of inaccurate P partitioning and precipitation within BioWin models of acid-phase digestion reactors. A BioWin configuration including an organic acid digester was parameterized and recalibrated based on the known traits of acid-phase digestion and then validated against a full-scale digester in a municipal wastewater treatment plant. This digester, with pH 5.14 and 61–74% solubilized P, was predicted by BioWin default parameters to have only 27% soluble P and a net formation of P precipitates. Corrections to the polyphosphate-accumulating organism decay, endogenous product decay, hydrolysis rate, and brushite behavior resulted in 67% solubilization with no precipitate formation. Cabinet configurations showed similar behavior when modified to include an acid-phase digester under default parameters, but predictions were similarly amended by our parameter changes. This improved modeling technique should allow operators to effectively characterize acid digesters for their own treatment trains and allow engineers to predict the performance of novel nutrient recovery technologies acting on acidogenic digest.

Eco-friendly and sustainability assessment of technologies for nutrient recovery from human urine—a review

Nitrogen (N), phosphorus (P), and potassium (K) represent the primary components of commercial NPK fertilizer and are primarily derived from finite resources through complex and expensive processes. To ensure global food security, the development of sustainable and eco-friendly procedures for fertilizer production has gained attention. Humans generally excrete urine containing 11 g of N/L, 0.3 g of P/L of P and 1.5 g of K/L, which benefit plant growth. The recovery of these essential plant nutrients from human urine has become the focal point of increasing research endeavors. Despite the potential advantages of nutrient recovery from urine, this process is complicated, and the economic implications are substantial. Furthermore, human urine may harbor undesirable contaminants, such as pathogens, pharmaceutical residues, hormones, and elevated salt levels, which could be disseminated into the environment through agriculture. This study appraised various emerging technologies for nutrient recovery from human urine, considering their challenges, environmental impact, economic viability, and the overall sustainability of the processes. This review elucidated that most nutrient recovery technologies demonstrated elevated efficiency in nutrient recovery. Nevertheless, a recurrent oversight involves neglecting the potential transfer of contaminants and pathogens into environmental matrices. The complexity of these processes and their economic feasibility vary, with some proving intricate and economically unviable. Given that no singular technology fully mitigates these challenges, integrating two or more technologies appears imperative to address drawbacks and enhance overall system performance.

Electrochemical Phosphorous Recovery from Wastewater: Modeling & Scale-up Considerations

The prospect of electrifying the recovery of valuable nutrients from waste streams is of great interest in the effort of reducing the overall energy consumption and environmental impact of nutrient usage. Currently, many electrochemical precipitation technologies exist, and some have shown energy consumption values on par with implemented nutrient recovery technologies (both gravimetric for specified products and volumetric for waste stream handling). However, electrochemical precipitation technologies are at low-to-intermediate Technology Readiness Levels (TRLs) and need to be optimized and scaled to determine the feasibility of implementing them industrially. This presentation discusses necessary considerations for modeling and scaling electrochemical precipitation technologies from the perspective of phosphorus (P) recovery.Two specific modeling tools were used to study P recovery as struvite. Mass transport and electrochemical phenomenon were modeled using COMSOL within a stirred batch reactor format. The COMSOL modelling yields valuable information about limiting conditions, spatial distribution of dissolved species concentrations, and the effects of various reactor conditions (e.g., stirring or applied potential). Next, the precipitation of struvite under various solution conditions is discussed with respect to a thermodynamic model of precipitation developed using OLI Flowsheets. The precipitation study is then discussed with respect to modeled reactor conditions to ascertain information relevant to scaling electrochemical P precipitation. Figures of Merit (FOM) useful in scaling electrochemical reactions are highlighted to alleviate the dependence on the reactor design used for modelling, enabling a transfer of information to other reactor formats.

Sustainable resource recovery and process improvement in anaerobic digesters using hydrochar: A circular bio‐economic perspective

AbstractHydrothermal carbonization (HTC) is a promising technology for waste valorisation and nutrient recovery to achieve sustainability. HTC converts organic waste into hydrochar, a carbon‐rich solid with numerous surface functionalities that can be used for energy and wastewater treatment. In this review, we highlight the potential of hydrochar‐based technology for improving the performance of anaerobic digestion (AD) systems and downstream applications of nutrient‐laden hydrochar. We identify knowledge gaps in hydrochar production, performance in AD systems and nutrient recovery, including the need for larger‐scale production facilities, multielement adsorption studies, and computational modelling. Techno‐economic analysis and life cycle assessment of hydrochar applications are critical to evaluating the commercial viability of this technology. Overall, hydrochar‐based technology offers a sustainable solution for waste management and resource recovery, with potential socioeconomic benefits for developing economies. The deployment of hydrochar‐based technology will directly address key issues highlighted in the United Nations' Sustainable Development Goals such as Clean water and sanitation (SDG 6); Zero hunger (SDG 2); and Climate action (SDG 13) thereby contributing to a more sustainable future.

Tuna sidestream valorization: a circular blue bioeconomy approach.

Tuna is an economically significant seafood, harvested throughout the world, and is heavily traded due to its high nutritional quality and consumer acceptance. Tuna meat is rich in essential nutrients such as amino acids, polyunsaturated fatty acids (PUFA), and trace minerals. The huge volume of solid and liquid sidestreams generated during the processing stages of tuna is creating environmental and socioeconomic challenges in coastal areas. Different products such as fish meal, protein hydrolysates, collagen, enzymes, oil, and bone powder can be produced from tuna sidestreams. Using different nutrient recovery technologies like enzymatic hydrolysis, chemical processing, and green technologies, various categories of product value chains can be created in line with the conventional processing industry. This review attempts to provide a route map for the tuna industry for achieving the circular blue-bioeconomic objectives and reorient the irregular utilization pattern into a sustainable and inclusive path.

Modeling an acid-phase digester in BioWin with parameter optimization from site data

Organic acid digesters are reactors of growing interest for municipal nutrient recovery technologies, but the industry standard BioWin modeling software does not accurately predict their performance. A BioWin configuration using default parameters will over-predict volatile fatty acid production in an acid digester, yielding an unrealistically low pH. We have characterized the effects of parameters for local pH inhibition thresholds, growth and decay kinetics, and hydraulic residence times to successfully facilitate more accurate modeling of acid phase digestion reactors in BioWin. These changes show improvements in a range of treatment train models without affecting accuracy in other reactors. Results were calibrated against a municipal acid phase digester to accurately predict pH, VFA concentration, and gas production. In particular, an acid digester with a measured suspension pH of 5.14 was predicted by BioWin using default parameters to exist at pH 4.35 with highly sensitive biogas methane content, but our parameter changes were able to correct the predicted suspension pH and VFA concentrations over a range of values. We also demonstrate that several intuitive or traditional parameters a BioWin user may attempt, such as growth and fermentation kinetics, do not yield meaningful results. Refinements incorporated into BioWin should allow future operators to easily model acid digesters for their specific treatment trains or allow users to predict changes while testing new wastewater treatment technologies.

Preliminary Study on the Preparation of Conductive Nanosized Calcium Carbonate Utilizing Biogas Slurry by a Synchronous Double Decomposition Coating Method.

Nanosized calcium carbonate (NCC) plays a vital role in the rubber and plastic fields as a filler, but it cannot resolve the electrostatic problem. Humic-acid-based NCC (HA-NCC) was accidentally discovered in the reaction between biogas slurry and calcium chloride (CaCl2), based on nutrient recovery and gradient treatment technology to solve the biogas slurry problem. A preliminary study on the preparation of conductive nanosized calcium carbonate (CNCC) from the HA-NCC was implemented. Meanwhile, a synchronous double decomposition coating method was proposed to properly explain the formation of HA-NCC in the biogas slurry. The CNCC was further obtained through drying and carbonizing the HA-NCC sample. The morphology of CNCC was a square shape with aggregation, and its crystals were calcite. The C content of CNCC was 5% higher than that of the normal CaCO3, implying a synchronous coating effect of soluble HA in biogas slurry on NCC. The weight loss of CNCC was about 2.5% at 630 °C, explaining why the HA-NCC remained black at 550 °C for 4 h. The CNCC was partly ordered and graphitized. The resistivity of the CNCC reached 2.62 × 106 Ω·cm. It could be used as a conductive powder. In view of the favorable characteristics described above, CNCC would be expected to be a filler and antistatic agent for plastics and rubbers to enhance the tensile and bending resistance of polymer materials, while eliminating electrostatic hazards. The results are also of great significance for developing high-end products to realize resource utilization of biogas slurry.

Resource-Oriented Sanitation: On-Farm Septage Treatment and Nutrient Recycling for Sustainable Agriculture in the Philippines

Nutrient recovery technologies have been constantly developed and optimised to address challenges in water and wastewater management, sanitation, and agri-food systems, while promoting sustainable management of resources and circular phosphorous economy. However, these technologies have been rarely explored beyond the laboratory-scale in developing countries where it is mostly needed. In this study, a nutrient recovery batch reactor system was installed at a local farm in the Philippines to process raw septage from an onsite sanitation system, a septic tank, to recover a high-value fertiliser for local crop production. The batch reactor was used for two processes, namely acid hydrolysis for pre-treatment of septage and chemical precipitation for recovered phosphorous fertiliser (RPF). The recovered fertiliser was then applied to produce eggplants and tomatoes, which are the common crops grown in the farm. Results show that an average of 290 g of RPF was produced for every 100 L of raw septage processed. With hydrolysis, 77% of the phosphate concentration were released as phosphates from the solid component of the raw septage. About 98.5% of phosphates were recovered from the hydrolysed septage. The RPF when applied to the farm’s eggplants and tomatoes has yields comparable to that of the commercial fertilisers. This study was able to demonstrate the potential of a resource-oriented sanitation system that promotes nutrient recycling towards sustainable agriculture that further leads to meeting the United Nations sustainable development goals, particularly zero hunger (goal 2), clean water and sanitation (goal 6), sustainable cities and communities (goal 11), and responsible consumption and production (goal 12).

Incorporation of main line impact into life cycle assessment of nutrient recovery from reject water using novel membrane contactor technology

Wastewater treatment plant (WWTP) nutrient recovery has recently gained traction in the search for new pathways for fertilizer production. In particular, concentrated waste streams such as reject water from sludge digestion are suitable. The environmental impact of a novel nutrient recovery technology using a membrane contactor (NPHarvest) was examined with an environmental life cycle assessment (LCA). Impact hotspots were benchmarked against a comparable technology (struvite precipitation and ammonia stripping), and the impacts of the two technologies were found to be similar for most studied environmental impact categories. To allow for the inclusion of effects on other parts of the WWTP while limiting the general system boundaries to the reject water treatment, a novel approach to capture the main line impact was developed. The effects on the main line contributed substantially to the overall results. The overall results indicated clear nutrient recovery benefits related to substituted materials in mineral fertilizer production. Additionally, reject water nutrient recovery provided even greater benefits due to reduced N2O emissions and the reduced use of precipitation chemicals in the WWTP main line. Nonetheless, both nutrient removal and recovery were necessary for the two technologies to reach a net zero climate impact in their current pilot scales. Further development of the NPHarvest technology—such as mitigating NH3 emissions, exploring alternative input chemicals and optimizing energy consumption (especially for crystallizing the ammonium salt solution that is produced)—is recommended before full-scale implementation.

Nutrient recovery through struvite precipitation from anaerobically digested poultry wastewater in an air-lift electrolytic reactor: Process modeling and cost analysis

Anaerobic digested poultry wastewater (ADPW) is characterized by high levels of nutrients (nitrogen and phosphorus), which need to be removed and recovered before the wastewater is discharged into water bodies with advanced nutrient recovery technologies that are cheap and eco-friendly. In this study, an innovative air-lift electrolytic reactor (ALER) with a magnesium anode was developed for phosphate (PO43−) and ammonia–nitrogen (NH3–N) recovery from anaerobically digested poultry wastewater through electrochemical struvite (MgNH4PO4‧ 6H2O) precipitation. Under constant current density (12.4 A/m2) and superficial velocity (107.42 m/h), the maximum removal efficiencies of PO43− and NH3–N were 99.9% and 97.3%, respectively. Kinetic modeling revealed that PO43− and NH3–N removal from the liquid phase by the ALER followed a pseudo-first-order reaction model, with rate constants (k) of 0.0188 min−1 and 0.0143 min−1, respectively. The recovered precipitate was characterized with FTIR, XRD, and SEM-EDS which also identified that precipitates as high-purity (88.5%) struvite with a mean particle size of 142.95 μm. Mean particle size and size distribution were found to be linearly increased with superficial upflow velocity. The electrical energy consumption per order (EEO) of the ALER was 0.824 kWh/m3, and the space–time yield is achieved at 0.988 kg/m3h with a corresponding operating cost of 3.87 $/m3. The ALER process has proven to be energy efficient in nutrient recovery from ADPW with struvite products suitable to be used in agricultural practices.

Energy Demand of Nitrogen and Phosphorus Based Fertilizers and Approaches to Circularity

The climate-related concerns associated with the manufacturing of synthetic fertilizers are largely traced back to energy and carbon emissions during the chemical manufacturing of ammonia. However, synthetic fertilizers are made up of several macronutrients (nitrogen, phosphorus and potassium), each with different energy intensities and environmental impacts. With the movement toward resource circularity, there is a need to create a more holistic view regarding the process energy associated with synthetic inorganic fertilizers, including nitrogen and phosphorus. Here, we first describe the growing production and consumption of inorganic (synthetic) and organic (animal waste) nutrients in agriculture as well as the process energy associated with the production of granular phosphorus and nitrogen-based fertilizers. Next, we present projected global demand of nitrogen and phosphorus nutrients based on various sustainability and societal equity scenarios to make an argument for nutrient recovery as a viable approach to meet this demand. Finally, we discuss the characteristics and challenges of emerging technologies for nutrient recovery along with baseline performance and costs of current operational recovery facilities.

Nutrient recovery technologies for management of blackwater: A review

Nutrient recovery and recycling are of great importance in sustainable development. Blackwater (BW) refers to wastewater from toilets, which contains feces, urine, water, and toilet paper from flush toilets. The highly concentrated nutrients of blackwater could be collected through source separation and treated adequately to recover nutrients efficiently and economically. The review intends to give an overview of the characteristics of BW and different techniques to recover nutrients and other valuable products. A number of these technologies are currently under development or being tested at laboratory or pilot scale. The perspective for blackwater nutrient recovery technologies is very positive due to their great potential. For application of source-oriented sanitation infrastructure and systems, there is still a long way to go for development of commercial technologies and valuable products.